Signaling system



Aug. 3, 1943. H. P. BoswAu' r v SIGNALING SYSTEM Filed June 10, 1940 4 Sheets-Sheet l 0 l b n Q 0. b. i 0| 3 b 0 I M 8m 8m N8 Em mw k Jwum HANS RBO3WA 1 Aug. 3, 1943. H; P. BOSWAU 2,325,829

SIGNALING SYSTEM Filed June 10, 1940 4 Sheets-Sheet 2 I o A E m w @EE fi I! s E jv/um HANS R 808 WAU,

H. P. BOSWAU SIGNALING SYSTEM Filed June 10, 1940 Aug. 3, 1943.

4 Sheets-Sheet 5 Jw a s O a P 6 H I 5 2 8h kwsruumk QRHQQ 2w M l- 1943- H. P. BOSWAU 2,325,829

SIGNALING SYSTEM Filed June 10, 1940 4 Sheets-Sheet 4 RADIO RECEIVER Patented Au 3, 1943 SIGNALING SYSTEM Hans P. Boswau, Lorain,

Lorain County corporation of Ohio Ohio, assignor to The Radio Corp.,

Lorain, Ohio, a

Application June 10, 1940, Serial No. 339,709 (01. 177-353) 8 Claims.

The present invention relates to signaling systems, and more particularly to a selective calling system for signaling a large number of subsidiary stations from one or more master stations or from one another.

The primary object of the invention is to provide a fast, simple and reliable selective calling system for signaling a large number (several thousand) of subsidiary stations, such as ship radio stations, from one or more master stations or from one another.

Another object is to provide a system of the character referred to which may operate satisfactorily over radio channels so as not to be affected by static noise or other signals.

Stillfurther objects are to provide a system for transmitting code ringing signals, after a ship is selected, to convey additional information with the call by giving one, two or three rings, short and long rings, etc.; to provide simple and sturdy apparatus consisting mainly ofsimple relays at receiving stations to eliminate costly and delicate selector mechanisms; and to provide a calling system which utilizes selective devices without electric locking circuits or mechanical holding pawls, etc. for maintaining the devices in advanced positions, thus providing devices which return to normal as soon as the signal ceases.

A still further object is to provide a system of the character referred to, except that there is an optional provision for making calls to groups of subsidiary stations, such as all ships of one fleet, or general calls to all subsidiary stations, such as distress calls.

Another optional provision of the improved system is to provide an arrangement at subsidiary stations for making general calls to all other subsidiary stations, such as distress calls, by means of an extremely simple sending device.

The final object is a still further optional provision at the subsidiary stations for selective calling of other subsidiary stations.

The invention will he better understood when reference is made to the following description and the accompanying drawings.

In the drawings:

Figure 1 shows an improved sending apparatus at the master station.

Figure 2 illustrates an arrangement of audio frequency generators at the master station which is alternative to the generators shown in Figure 1.

Figure 3 shows the improved sending apparatus at the subsidiary station, while Figure 4 illustrates a modification of the individual tuned relays shown in Figures 5 and 6.

Figure 5 shows the receiving apparatus at the subsidiary station.

Figure 6 shows a system similar to Figure 5, except that there is a provision for fleet and general calls.

In order to call a particular ship, the carrier wave of the radio transmitter at the master station is modulated by a selective ringing signal, which consists of a number of successive pulses of different audio frequencies. In the preferred arrangement seven audio frequencies, ranging from to 300 cycles, are used and five successive impulses are transmitted. In addition, an eighth audio frequency may be used for a general call. The successive pulses of the various audio frequencies constituting the selective signal are transmitted without intervening pauses, i. e. the modulation is switched from one audio frequency to the next one instantaneously. This means that two successive audio frequencies. Therefore, the total number of possible combinations for five pulses of seven different frequencies is 7 6 6 6 6 or .9072. However, the code ringing feature incorporated in the system excludes certain of these codes, viz. all thos which use the same frequency for the third and for the fifth pulse. This leaves a total of 7560 distinct codes, 840 of which make use of three different frequencies per code, 4200 require four frequencies and 2520 employ five frequencies.

At the receiving end on the ships the audio frequency pulses are received on relays having reeds tuned to the different audio frequencies employed in the code for the particular ship. Ships with a code using three different audio frequencies have three tuned reed relays, etc. When the reed relay corresponding to the first audio frequency of the ships code is excited by the transmission of this frequency from another station, the reed vibrates and intermittently closes a contact operating an ordinary telephone relay. The latter in turn, prepares a circuit from the second reed relay to another telephone relay, and this process is continued until the last pulse is received, whereupon a circuit is closed for a bell or any other type of signal as may be desired.

At the master station the radio transmitter H9, with antenna 120 and ground 12!, is normally connected through the key I09 to the telephone circuit H0, over which the speech to be transmitted is received. To call a ship the operator manipulates the key I09 to connect the transmitter H9, through the transformer I08, to the keys I00 to I01 and Ill to H1. Keys Hi to pulses must be of different I I1 are mechanically interlocked so that when a key is operated, it is latched until another key is operated, whereby the first key is released. A release key. indicated at I I8, serves to restore the last operated key to normal. Keys I to ID! are non-locking and do not release the keys III to H1.

In order to call the ship with the code 12342, illustrated in Figure 5, the operator pushes key I II, which stays latched. This closes a circuit from the generator 20I, producing audio frequency No. 1, through key I I I and the break contacts of keys IOI to I0! to transformer I08 and back to generator 20L As a result, transmitter H9 is modulated with frequency No. 1. On the ships, the modulated carrier wave is received by the receiver I9 over antenna 520 andground 52 I. The receiver demodulates thi carrier wave, with the result that the receiver puts out audio frequency No. 1 over switch-hook 509, filter 5I1, transformer 508, to the windings of reed relays 5 to 5I4 in series. The reed armature 523 of the relay 5| i is tuned to this audio frequency and vibrates'in response thereto. intermittently closing contact 524. The reeds of relays 5I2, M3 and 5I4 are tuned to different audio frequencies and therefore do not respond.

The intermittent closure of contact 524 cccurs once er cycle of the audio frequency, or

120 to 300 times per second. and then only for a relatively small fraction of each cycle possibly five to ten percent of the time. This is not sulficient to operate an ordinary telephone relay directly, but may be used to charge a relatively large condenser, which discharges through the telephone relay while contact 524 is open and thus provides sufficient current to operate the relay. Every time contact 524 closes, current flows from the ship's dynamo 504 over reed 523, contact 524. resistance 525. terminal Fl, jumper connection 520. terminal PI. winding 529 of telephone relay 50I. break contacts 530 and 53I of relays 502 and 503. back to dynamo 504. At the same time condenser 526 is charged from 504 over 523, 524, 525 to 526, and back to 504. Every time contact 524 opens. condenser 526 discharges FI, 528, PI, 529, 530, 53l back to .526. a

Resistance 525 is provided to prevent excessive sparking at contact 524. but is of'low enough ralue to cause no appreciable delay in the char ing time of the condenser 526. Condenser 505 is of large capacity andQby providing the equivalent of a source f voltage within the selective device, serves to eliminate the inductive effect of the conductors from the dynamo 504 to the selective signaling device. which efiect may be sufficient to delay the char ing of the condenser 526. As a result of all these provisions, every time contact 524 closes, condenser 526 is charged almost instantaneously to the full voltage of dynamo 504, and during the time contact 524 is open the condenser discharges throu h the relay 50I. The combined effect of the current flowing through the relay 50I directly from the dynamo 504 as long as contact 524 is closed. and of the condenser discharge. is to operate the relay. This relay and also relays 502 and 503 are provided with a copper sleeve around their cores to make them slow releasing, so that they will not release during brief interruptions of the operating current.

Thus the ultimate result of the various functions is that relay 50I operates in response to relay 5| l, and remains operated a long as freover vibrate. Bleeder resistance 521 is of considerably higher value than the winding 529 of relay 50I, and therefore will have no appreciable efiect on the current flowing through the relay. Its purpose is to insure the discharge of condenser 526 to prevent subsequent false operations when the circuit through the winding 529 is subsequently opened by the contact 530. The operator at the master station now pushes key H2 which releases key I I I, opening the circuit of the generator MI and closing instead a circuit for generator 202. This substitutes audio frequency No. 2 for No. 1 without any appreciable intervening pause.

On the called ship the reed relay 5 ceases to vibrate while reed relay 5I2, which is tuned to audio frequency No. 2, begins to vibrate, intermittently closing contact 532. This charges condenser 534 and closes a circuit over terminal F2, jumper 535, terminal P2, winding 533 and make contact 536 of relay 50I and winding 53'! of relay 502. The result is that relay 502 operates and relay 50I remains operated. Relay 502 opens the original circuit through winding 529 of relay 50I and prepares a new circuit for winding 538 of relay 502. At the master station, key H3 is now operated, with the result that frequency No. 3 (from generator 203) is now transmitted. On the called ship, reed relay 5I2 stops and reed relay 5I3 starts to vibrate. This opens the circuit through windings 533 and 531 of relays 50I and 502, and closes a new circuit over F3 and P3 through winding 538 of relay 502. causing relay 50I to releas and holding relay 502 operated.

Next the master station'operator pushes key II4, thereby substituting audio frequency No. 4 for No. 3, with the result that on the called ship reed relay 5I3 stops and reed relay 5I4 starts to vibrate, opening the circuit through winding 538 of relay 502 and closing a new circuit over F4 and P4 through the winding 539 of relay 503, make contact 54I of relay 502, break contact 536 of relay 50I and winding 53? of relay 502. Relay 503 operates and relay 502 is held over this circuit. The operator at the master station is now ready to ring the called ship. To do this he pushes key I02, which is non-locking and which does not release key I! (or any other key III-Ill). As long as key I02 is pushed, audio frequency No. 2 is transmitted instead of No. 4, and when the operator releas es key I02, No. 4, will again be transmitted.

On the called ship the transmission of frequency No. 2 instead of No. 4 causes reed relay 5I4 to stop and relay 5I2 to start. This opens the circuit through windings 539 and 531 of relays 503 and 502 and closes a new circuit for 'the circuit through the winding 540 of relay 503 and again closing the above described circuit for winding 539 and 537 in series, except that contact 542 of relay 503 takes the place of 54I of relay 502, which is deenergized at this time. Relay 502 operates in series with 503 and opens the bellcircuit at contact 545.

The operator may now ring the bell 506 as often and as long as desired by manipulating the bell circuit can example. to give key I02, the bell ringing as long as key I02 is depressed. When he has completed the call, he operates release key II8, which restores key H4 and returns key I09 to normal. As a result, relay on the called shi ceases to vibrate, causing the release of relays 502 and 503 and thereby restoring the receiving equipment to normal. In response to the call the operator on the called ship may lift his telephone, operating switchhook 509, which disconnects the receiver output from the selective calling equipment and connects it instead to the telephone line 522. All other ships have codes differing from that of the called ship, so that in the sequence of frequency transmissions a point will be reached on overy other ship where the transmitted audio frequency does not correspond tothe one needed to keep the selection relays SM, 502 or 503 onergized. These relays therefore release before be completed. It is to be noted that the described condenser charge and discharge arrangement makes it possible to operate ordinary slow releasing telephone relays directly from reed contacts vibrating at 120300 cycles and to keep these relays operated as long as the audio frequency is received by the reed. This feature, in conjunction with the fact that the switching from one audio frequency to the next occurs almost instantaneously, so that the next selection relay circuit is closed, before the preceding relay has released, does away with the need for locking circuits for the selection relays and provides a device which automat cally releases and returns to normal soon after the selecting signals cease. This avoids the possibility of leaving the device in a partially advanced stage. It will be noted that the last two audio frequencies of a code are transmitted alternately to produce code-rings on the called ship. For two rings, on the call described above, the code transmitted would be 12342-42-4. It will be seen that this code would operate selecting devices having codes such as 42424, 34242 or 23424. In all these codes the third and fifth pulse use the same frequency and it will be evident why such codes must be excluded.

Filter 5 I I is an inexpensive low pass filter which freely passes audio frequencies of 300 cycles and less, but cuts off frequencies above 300 cycles. This filter prevents the greatest part of atmospheric static noises from reaching the reed relays, and also cuts down the normal speech currents to a negligible amount, whereas the selective audio frequencies in the range from 120 to 300 cycles are freely passed.- The result is a marked improvement of the signal to noise ratio in the windings of the reed relays, making it possible to operate the selecting device through considerable interference. The reed relays, being responsive only to certain predetermined frequencies, are not affected-by the small amount of static and speech passing through filter 5I'I, so that the selective device will not respond to any noise or speech other than the proper selection code.

Figure 5 shows four reed relays, but only three are required for codes using three frequencies, whereas codes using five frequencies require five reed relays. The contact circuits of the reed relays are wired to terminals FI to F4, while the pulse receiving relays 50I to 503 are connected to terminals PI to P5. This arrangement makes it possible to cross-connect the terminals as required for the various code patterns.

Figure 6 shows selective receiving equipment I similar to Figure 5 and for the same code, but inthe microphone eluding provisions for fleet calls and a general call. Reed relays 6I5 and BIG correspond to re-- lays 6H and 6I3, but respond to different audio frequencies. The selection code for Figure 6 may be 12342. The following codes all have the same second, fourth and fifth digit, differing only in the first and third digits:

Now, if relay 6I5 responds to frequency No. 7 and 6| 5 to frequency No. 6, the code 72642 can be used as a fleet code for the nineteen other codes in this group. In other words, relays 6H and BI3 on the various ships respond to different frequencies as indicated by the above given codes. Relays BI2 respond to frequency No. 2 and 0H to No. 4 on all ships, and also relays 6I5 to frequency No. 7 and BIG to No. 6 on all ships. With this arrangement, all nineteen ships in the fleet can be called simultaneously by using code 7.2642. These codes use four different frequencies. In a similar manner codes using only three different frequencies can be arranged in groups of thirty for fleet calls, i. e. twenty-nine ships can be called simultaneously with the fleet call.

In addition, Figure 6 shows a reed relay 3I0 with its associated telephone relay 600 and a bell 607 controlled by the latter. This bell rings whenever reed relay 6 I 0 is operated, and provides a general call for all ships equipped with this feature. To make a general call from the master station. the operator depresses non-locking key I00, after operating key I 09, thereby connecting generator 200 to transmitter IIS, which then emits a carrier wave modulated by the frequency of generator 200. Reed relays 6I0 on all ships are tuned to this same frequency, so thatbells 601 will ring on all-ships receiving the generav call signal. The general call can, of course, be provided without the fleet call, if desired. In that case relays [H5 and BIG in Figure 6 would be omitted. A separate bell 601 for the general call is shown, as would be desirable where it is used exclusively for distress purposes. Where this is not the case, relay 600 can control the same bell $06 as the selective relays. In Figure 6 all relays and connections not specifically referred to hereinbefore have the same reference characters as the-corresponding relay or connection in Figure 5 except that the first number of the character has been changed to 6 to accord with the figure number.

Figure 3 shows one embodiment of transmitting equipment on a ship. The radio transmitter is indicated by 4I9 with antenna 420 and ground connection Hi. When the ship operator lifts his telephone to talk, switch-hook 423 closes a circuit from battery 422, through microphone 409,

break contacts of keys 400-401 and transformer 4 I8, back to battery 022. The secondary of transformer 4i 8 is connected to the input circuit of transmitter 4I9, so that the words spoken into 409 will be transmitted. Key 400 is a non-locking key provided for making general calls to all ships. Keys I to 401 are mechanically interlocked keys, restored by each other and by release key 408. ie devices shown generators 200-207. The equipment inclosed in a ship is not desired. Thus, for making general or distress calls, the only equipment required, in addition to the normal radio telephone transmitting apparatus, is key 400 and vibrator M0.

To make a general call, for instance, the ship operator lifts his telephone and operates key 400, which disconnects microphone 409 and starts vibrator M0. The interrupted current produced in this manner, by passing through transformer M8, modulates transmitter M9 with the audio frequency assigned to the general call, thereby operating relays M and 600 and bell 601 on all ships receiving the call. For selective calling the operator presses the keys ADI-401 in the proper sequence for producing the desired code, and then restores the last operated key by means of release key 408. As a result vibrators till-BIT are operated in succession to produce the required audio frequencies for selecting the desired ship.

In the foregoing it is assumed that the reed relays are tuned to frequencies in the range of from 120 to 300 cycles. If desired, the mechanically tuned relays can be operated at lower frequencies, e. g. at the frequencies commonly in use for harmonic or synchronic selective ringing in telephone exchanges. These frequencies range from 16 to 66 cycles, and relays responding to them are in general use. In that case, it is proposed to use the arrangement shown in Figure 2, where 308 represents a generator producing a frequency of 300 cycles, The output of this generator is connected to keys l00-l 01 and Ill-H1 through commutators 300-307, driven by the motor 309. Each of these commutators interrupts the 300-cycle current of generator 308 at one of the desired frequencies between 16 and 66 cycles, or whatever other range is chosen. The result is that transmitter H9 emits a carrier wave modulated by a series of 300-cycle impulses, these impulses being emitted at the rate determined by the commutator (300-307) selected oy'the operated selection key.

The receiving apparatus on the ships is the same as shown in Figures 5 and 6. except that the tuned relays 5 to 5M and 610 to SIB would be tuned to frequencies in the desired range, e. g. 16-66 cycles, and that a rectifier of any of many Well known types is interposed between filters 5!! or (ill and transformers 508 or 608, as indicated at 5|8 or 618. These rectifiers transform the series of 300-cycle impulses into a pulsating or alternating current of a frequency corresponding to that of the selected commutator (300-307) Series of 300-cycle impulses are proposed instead of direct transmission of frequencies in the 16-66 cycle range, because radio transmitters and receivers capable of responding to such low frequencies are relatively expensive, and because the noise and speech elimination effected by filters 5H and 6H is better at 300 cycles. In the figures each tuned reed relay is shown with an individual operating Winding. It is possible, however, to have a common operating winding and armature on which the various tuned reeds are mounted, in a manner analogous to the wellknown Frahm frequency meter. Such an arrangement is shown in Figure 4.

Where the ships are equipped with selective calling transmitters, as shown in Figure 3, they may also call the master or shore stations selectively, providing the latter are equipped with the same selective receiving devices as the ships. The proposed system can also be used on land telephone lines, such as train dispatching lines, where a large number of stations are connected to one relatively long telephone line. The foregoing describes a. system using seven selection frequencies and five pulses, but obviously fewer or more frequencies and fewer or more pulses may be employed, depending upon the total number of distance codes required.

Cons CALCULATIONS 1. General formula for total number T of all possible codes where n is the number of frequencies and p the number of pulses. For the first pulse any one of the n frequencies may be chosen, but for the remaining p-l pulses the frequency of the immediately preceding pulse cannot be used, leaving n-l choices for these p-l pulses.

For seven frequencies and five pulses:

2. Two-frequency codes (using only two of the seven frequencies per code) Number of permutations of seven elements taken two at a time:

No matter how many pulses are used, two-frequency codes can be arranged in only one pattern, viz. a h a b a. In this pattern the third and fifth pulse are the same, therefore these forty-two codes are excluded in view of the limitations imposed by code ringing.

3. Three-frequency codes Number of permutations of seven elements taken three at a time:

For five-pulse codes, some of the three frequencies must be repeated, there being two combinations possible: a a a b c and a a b b c. The first of these can be arranged only in one pattern a b a c a which has identical third and fifth pulses and must therefore be excluded. The

The last two patterns must be excluded because r the third pulse is the same as the fifth. This leaves four patterns available or 210 4=840 usable three-frequency codes. quency codes (seven patterns) 210 7=1470.

4. Four-frequency codes Number of permutations of seven elements taken four at a time:

Only one combination is possible for five-pulse codes: a a b c d, which can be arranged in six patterns:

a b a c d a b c a d a b c d a bi a c a d bacda bcada The last pattern has the same third and fifth pulse and must therefore be excluded, leaving Total three-frefive available patterns tour-frequency codes.

Total four-frequency codes (six patterns): 840 6=5040.

5. Five-frequency codes Number of permutations of seven elements taken five at a time: Y

X6 5 4 3=2520 There is only one possible combi r 84Q 5=4200 usable nation and pat '7. The number of five-pulse patterns, total and usable, remainsthe same for any number of frequencies from five on up; only the number of permutations chariges. Increasing the frequencies from seven t eight would provide the following codes:

Total Usable 'lype Permutations P t P t a a terns Codes tern Codes 2-frequency 8X7 56 l 56 3-frequencyun. 3X7X6 336 '7 2352 4 1344 4-irequcncy 8 7 0 5 =l680 6 10080 8400 5-irequency 8 7 6X5X4=6720 l 6720 l 6720 Total. 19208 16464 8. For codes using seven frequencies and six pulses. the number of patterns increases as shown below, while the number of permutations remains the same:

IIotal Usable Type Permutations P t P t I terns Codes tems Codes 2-lrequency 7X0 42 1 42 3-frequency- 7 6X5 210 15 3150 8 1680 i-frequency. 7X6 5 4 840 25 21000 20 16800 5-irequency, 7X6 5X4 3 =2520 10 25200 9 22680 6-lrequcncy. 7X6 5 4X3X2=5040 1 5040 l 5040 Total 54432 46200 It is apparent from the foregoing calculations, which are set forth purely by way of example, that the invention is not limited to codes of any Particular number of digits or frequencies, but fistead is sufficiently broad to embrace any desired number of digits within a code, or any desired frequency or frequencies, and the only c ange necessary in,this case is to have a greater or less number of reedrelays in the receiving cirthose me 5 ance with the desired transmitted code and frequencies, and such changes will readily occur to rely skilled in the art after consideration otthe foregoing explanatory calculations and the principles of the invention, as set forth hereinbefore'.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is: I

1. In combination, a plurality of circuit controlling reeds each responsive to a different frequency, means including a receiving system for selectively causing said reeds to vibrate in succession in accordance with successively received frequencies, a plurality of relays, each relay having a plurality of windings and each relay having circuit controlling armatures common to its plurality of windings and operated when any one of its windings is operated, connections for energizing the windings of the relays from different circuit controlling reeds in different combinations but for energizing the different windings of the same relay from different reeds, said connections including the circuit controlling armatures of the different relays in permutation and a final signaling circuit closed by the successive operation of the windings of relays in a given order,

2. In combination, a plurality of circuit controlling reeds each responsive to a different frequency, means including a receiving system for selectively causing said reeds to vibrate in succession in accordance with successively received frequencies, a plurality of relays, each relay having a plurality of windings and each relay having circuit controlling armatures common to its plurality of windings and operated when any one of its windings is operated, connections for energizing the windings of the relays from different circuit controlling reeds in different combinations but for energizing the different windings of the same relay from diiferent reeds, said conedits and a corresponding number of slow rel'tise relays which actuate the make and break contacts for energizing one or more ringing ciricuits, depending upon whether it is a fleet, a general call or individual call. The number of alternators or reed transmitting elements at the sending stations would be modified in accordnections including the circuit controlling armatures of the different relays in permutation, and a final signaling circuit; closed by the successive operation of the windings of the relays in a given order, said circuit being also thereafter adapted to be intermittently closed 'by the operation of one of said reeds other than the last reed to be operated in succession.

3. In combination, a plurality of circuit c0ntrolling reeds each responsive to a dillerent freq en y, m ans including a receiving system for selectively causing said reeds to vibrate in succession in accordance with successively received frequencies, a plurality of relays, each relay having a plurality of windings and each relay having circuit controlling armatures common to its plurality of windings and operated when any one of its windings is operated, connections for energizing the windings of the relays from different circuit controlling reeds in different combinations but for energizing the different windings of the same relay from different reeds, said connections including the'circuit controlling armatures of the different relays in permutation, and an indicating device responsive to the successive operation of the windings and responsive selectively to both the last reed of the successively operated group of reeds and also responsive to a reed other than the said last-mentioned reed.

- HANS P. BOSWAU. 

